Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare destructiveHint=true, readOnlyHint=false and idempotentHint=false, so the agent knows this mutates state. The description adds nothing about reversibility, whether other users' reactions are affected, or permission requirements, and it does not contradict the annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the action, which is good, but the post_id guidance block (resolver list plus 'Never pass' list) is repeated almost word-for-word from the schema, so several sentences are spent restating structured data rather than adding value.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 3-param, no-output-schema mutation tool with full annotation coverage, the description supplies the one thing structured fields do not: how to obtain a valid post_id and what must never be substituted. Return behavior is left implicit, but that is a minor gap given annotations cover the safety profile.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents post_id, reaction and account_id in detail. The description's post_id text is essentially a verbatim duplicate of the schema field, adding no new syntax or format meaning; baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb+resource ('Remove the user's reaction from one exact post') and scopes it to a single post. It implies the boundary against post-comment and message reaction siblings but never names an alternative, so an agent must infer the routing itself.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives explicit procedural guidance ('Resolve post_id first') and a clear prohibition ('never use post URL/text unless another resolver explicitly converts it'), with concrete resolver paths. It stops short of stating when-not to use this tool versus sibling reaction tools, so no explicit exclusion list.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.